This invention relates to an apparatus for sampling blood, and more particularly, to an apparatus to be integrally mounted in the tubing of a blood pressure monitoring system for safely and efficiently obtaining blood samples from patients.
In intensive care units, trauma units, and other medical facilities at hospitals, a catheter inserted into an artery of the patient is used for continuously monitoring blood pressure and obtaining blood samples. These patients typically have poor arterial access, are clinically unstable, and require continuous monitoring. Frequent blood sample analysis is also required.
When a patient has an arterial catheter, all blood samples tend to be drawn by accessing the line from the catheter to the monitoring devices rather than puncturing the patient's skin with a needle each time a blood sample is required. Drawing the blood samples from the arterial line is less painful for the patient and more convenient for the medical personnel.
A number of techniques are currently used for drawing blood from arterial lines. The existing techniques have not achieved the results desired by the medical staff and patients. In several systems, a significant portion of the blood drawn from the patient must be discarded in attempts to obtain a pure sample. The frequency of blood drawing and the amounts being drawn can pose a significant problem for certain patients, especially the elderly and the very young.
Infection is another serious problem with the existing techniques for drawing blood. Any break in the skin of the patient or any breaks in the monitoring system connected to the catheter serve as portal of entry for bacteria. The blood sampling systems currently in use provide a portal of entry for bacteria.
In recent years, medical personnel have faced a significant risk of contracting blood borne infections when using needles and in the general handling of the blood. Improved blood drawing systems are needed to reduce the chance of needle sticks and to eliminate any blood spillage.
The most common method for withdrawing blood from pressure monitoring lines involves the use of stopcocks and syringes. The stopcock is placed approximately 12 inches from the insertion site in series with a catheter, a transducer on the pressure monitoring system, and a saline supply. A port disposed on the side of the stopcock is used for blood sampling.
When the stopcock is turned to open the side port, the saline supply is temporarily stopped. A syringe is used to withdraw the saline and small amounts of blood from the tube and the catheter. Once the blood is drawn through the catheter and the tube to the side port of the stopcock, a second, heparinized syringe is inserted to withdraw the sample of blood. The stopcock is then turned to block the flow from the catheter and open the flow to the saline solution to flush out the side port. The stopcock is turned again to block the side port and connect the saline supply to the catheter, and to continue monitoring the blood pressure of the patient.
The stopcock system requires a number of manipulative steps in order to obtain the blood sample. The opening of the side port increases the possibility of contamination and infection of the patient's blood. Blood usually drips from the side port after the sample is drawn and blood residue may remain on the side port, even after the saline flush of the interior of the side port.
Other methods for obtaining a blood sample include T-connectors or rubber injection ports at the catheter insertion site. These systems can also result in a dilution of the blood sample. Dilution of the sample leads to inaccurate results. The tendency is to repeat the sampling and testing procedures, which increases the costs, time, risk of contamination, and patient blood loss.
Medical personnel desire an improved means for drawing blood samples because of the large amount of blood drawn daily and the potential problems associated with blood drawing.